You can update a mailbox password at any time by following these steps ...
Log into the Reseller Zone at https://my.ezyreseller.com.au
Click the Quick Server Login button for your Hosted Organisation from the Dashboard.
A new browser window will open and you will automatically be logged into Cloud Control at https://manage.cloudcontrol.net.au
Click the Mailboxes icon.
Click into the mailbox for which you're changing the password.
Click the General tab, then enter your new password in the relevant fields.
Finally, click the Set Password button.
It may take a couple of minutes for the change to fully replicate through Active Directory, but in most cases, the change will be active immediately.